This invention relates to a process for forming a multilayered, high resolution recording medium having a plurality of reflecting layers separated by a spacing layer.
As disclosed in West German DT-OS No. 26 58 623, high resolution, multicolored recording media can be formed by means of multiple, carefully formed reflecting layers separated by a translucent spacing layer. According to the teaching of this patent specification, the reflecting layers are formed by means of a high frequency sputter etching process. In this process a substrate is exposed to a high vacuum in a vacuum apparatus and then coated by means of a cathode formed of a material such as silver which is suitable for the generation of reflecting layers. Thereupon, the reflecting layer is coated with a photosensitive layer and the photosensitive layer is exposed through a patterned exposure mask. After the unexposed pattern portion of the photosensitive layer has been removed, the patterned portion of the reflecting layer not covered with the photosensitive layer is then removed by ion bombardment with reversed polarization.
The process disclosed in DT-OS No. 26 58 623 presents the disadvantage that in addition to the ions responsible for the material removal there also arise high energy electrons. During the removal process, these energy-rich electrons often bring about a chemical alteration of the remaining photosensitive layer in the form of a hardening of the photosensitive layer by cross-linking. The hardened photosensitive layer is not removable in the form of a true solution as is the photosensitive layer prior to hardening. When the hardened photosensitive layer is immersed in solvent it tends to swell rather than dissolve, and the removal of the photosensitive layer often has to be initiated by mechanical means such as ultrasound or wiping techniques. On many occasions, such techniques may damage the underlying remaining reflecting layer, which is quite thin and easily damaged, often having a thickness of only a few atomic layers. During the production process such a removal of the remaining photosensitive layer is required several times, and the spoilage rate can therefore climb appreciably.